Infection of wounds is a major source of healthcare expenditure in the United States. Approximately 5% of all surgical wounds become infected with microorganisms, and that figure is considerably higher (˜10-20%) for patients undergoing abdominal surgery. Bacterial species, such as Staphylococci, are the most frequently isolated organisms from infected wounds. This is probably because humans are the natural reservoir for Staphylococci in the environment, with up to 50% of the population colonized at any given time. Colonization rates are significantly higher in the hospital setting, both among healthcare workers, and among patients. Moreover, the colonizing organisms in the hospital environment are likely to be resistant to many forms of antimicrobial therapy, due to the strong selective pressure that exists in the nosocomial environment, where antibiotics are frequently used. Staphylococci are usually carried as harmless commensals, however given a breach in the epidermis, they can cause severe, even life threatening infection.
Staphylococci are the most common etiologic agents in surgical wound infections; others include, but are not limited to, Streptococcus pyogenes, Pseudomonas aeruginosa, Enterococcusfaecalis, Proteus mirabilis, Serratia marcescens, Enterobacter clocae, Acetinobacter anitratus, Klebsiella pneumoniae, and Escherichia coli. 
Post-surgical infection due to microorganisms is a significant concern of hospitals. The most common way of preventing such infection is to administer prophylactic antibiotic drugs. While generally effective, this strategy has the unintended effect of breeding resistant strains of bacteria. The routine use of prophylactic antibiotics should be discouraged for the very reason that it promotes the growth of resistant strains.
Rather than using routine prophylaxis, a better approach is to practice good wound management, i.e., keep the area free from bacteria before, during, and after surgery, and carefully monitor the site for infection during healing. Normal monitoring methods include close observation of the wound site for slow healing, signs of inflammation and pus, as well as measuring the patient's temperature for signs of fever. Unfortunately, many symptoms are only evident after the infection is already established. Furthermore, after a patient is discharged from the hospital he/she becomes responsible for monitoring their own healthcare, and the symptoms of infection may not be evident to the unskilled patient.
A method, system, or biosensor that can detect the early stages of infection before symptoms develop would be advantageous to both patients and healthcare workers. Such a method, or biosensor, should be sensitive to low levels of microorganisms present in a wound to facilitate early detection. If a patient can accurately monitor the condition of a wound after discharge, then appropriate antimicrobial therapy can be initiated early enough to prevent a more serious infection.